Method of etching metals



Jan. 10, 1956 R. w. MICHLER 2,730,435

METHOD OF ETCHING METALS Filed oct. 4, 1954 /4 /4 1N VEN ToR.

UnitedStates Patent O 2,730,435 METHOD orV Ercmno s RobertW. Michiel, Penis, Calif. l tppngrin ofqber 4, :1954,1 serial No. 459,947

' 3 Claims. (Ch 41 43) This invention relates to a method of etching metals,

l andis:particularlysuitable for etchingferrousmetals andy aluminum and itsalloys.

t A primary object of the invention is yto lprovide a simple. and non-toxic method whereby'metals may be permanently etched with indicia or designs.

"Explanatory, of the present invention therelare many situations', wherein it is desired to mark. a metal with-an indieatingmediumor ornamentaldesign. Insorner instances these metals may have been hardened to a very high degree. As a typical example thickness gauges have, been provided, having blades of various ,thicknesses and thesel blades have been appropriately hardened ,so as tof'r'etain their thicknesses while undergoingwear. The indiifidualblades .have indicia, etched thereon indicating thethicknesses thereof. Whenthe blade, hasbeen hardenfedmit'fis rsometimes very difficult to engrave on the blade the indici'al signifying the blade thickness. Inlieu Athereof acids and similar chemicals have been used to etch the indiciaony theblade. These.acidsorchemicals that have heretofore" been used are" objectionable because v they are frequently dangerous to handle and usually are quite toxic. The` application` of indicia or designs to bladesof a;thickness gauge, is but one of a largenumber of instances where it is desired to apply the designs or indicia to a polished metal surface which may or may not be hardened.

With the foregoing and other objects in view, which will be made manifest in the following detailed description and specifically pointed out in the appended claims, reference is had to the accompanying drawings for an illustrative embodiment of the invention, wherein:

Figure 1 is a sectional view of a thickness gauge blade illustrating the ground deposited thereon in accordance with the present invention;

Fig. 2 is a sectional view on an enlarged scale illustrating the ground as having been stamped in accordance with the indicia or design that is to be applied to the face of the blade;

Fig. 3 is a view similar to Fig. 2, illustrating the condition of the ground and blade after the ionic exchange has taken place in accordance with the present method;

Fig. 4 is a sectional view similar to Fig. 2, showing the blade in its finished condition; and

Fig. 5 is a top plan view of a portion of the blade shown in Fig. 4.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, indicates a blade of a thickness gauge which is usually formed of an iron alloy and suitably hardened. The top and bottom surfaces of the blade are ground and polished in accordance with conventional practice. On that area of the blade which is to have the indicia or design applied thereto I apply a rst ground layer 11. This lower or iirst ground layer consists of natural ozokerite dissolved in a non-toxic solvent such as benzine. Ozokerite is a natural mineral wax and I prepare the solution by grinding the ozokerite into tine particles and 2,730,435 Batented Jan- 10, .1.95.61

- placing approximately grains of ozokerite in l fluid ounce of benzine. In approximately 24 hours about live grains of ozokerite willv dissolve in the benzine. This solutionis painted or-otherwise applied to the` surface of the blade 10, and due to the volatility of the benzine, the solvent quickly evaporates leaving a thin iilm of ozokerite over the area. If conditions are such that toxicity is no objection solvents such as carbon tetrachloride or sulphuric ether. may be employed. Usually, however, benzine is found to be a relatively inexpensive and nontoxic solvent which srhighly desirable.

As soon as the solvent for the ozokerite has evaporated I apply a second ground layer 12 thereover. This ground layer consists of gilsonite dissolved ina non-toxic solvent such as benzine. Approximately 15 grains ofgilsonite in powered form are dissolved in 1 iiuid ounce of benzine. As soon as the benzine or solvent for the gilsonite evaporates a second or overlying thin film of gilsonite is provided. Thesetwo layers together constitute the ground on which the indicia or design may be formed.

lf the indicia or design is in the form of a letter or numeral I may employ standard printers metal type for this purpose as per formula of American Type Formula. The faces of such type are merely pressed against the surface of the ground causing portions of the ground immedately therebeneath to adhere to thev type and to be withdrawn bodily from the ground, thus leaving small openings 13 extending` therethrough to the upper surface tothe blade 10. The material of the ground adheres to the type and is withdrawn from thepground thereby. The nature of .s the.v ozokerite Viilrn facilitates separation of the ground from the surface of the blade and is conducive to the formation oflthe openings 13 with very sharp and regular edges in conformity with the shape of the type. After the openings 13 have been formed in the ground in conformity With the shape of the type an aqueous solutionof cupric chloride to which a small amountof isopropyl alcohol is added is applied over the ground. The aqueous solution of cupric chloride merely provides a copper salt supplying cupric ions which may exchange with the iron in the body of the blade 10 in conformity with the well-known ionic exchange between cooper salts and ferrie bodies. The isopropyl alcohol merely functions as a wetting agent reducing the surface tension of the aqueous solution of cupric chloride and causing it to spread evenly over the upper film of gilsonite. As long as the aqueous solution of cupric chloride remains in place an ionic exchange takes place through the exposed portions of the blade 10 that are exposed by the openings 13 with the result that small depressions 14 are formed in the surface of the blade in conformity with the shape of the openings 13 in the ground. Copper is deposited in the openings 13 as indicated at 15. Usually the cupric chloride solution is allowed to remain in place from thirty seconds to two minutes, depending upon the depth of etch that is desired on blade 10. The extent to which the blade has been etched by the ionic exchange can, to some extent, be determined by observing the color at the bottoms of the openings 13 through the layer of cupric chloride solution. When the blade has been etched to the desired depth the reaction is arrested by dropping onto the cupric chloride solution a small amount of liquid ammonia. Thereafter, the entire ground and deposited free copper can be wiped oif of the blade by a cotton swab soaked either in benzine or in inexpensive mineral oil, such as fuel oil. This wiping action not only removes the ground but usually removes copper from the recesses 14, thus leaving the design or indicia permanently etched on the surface of the blade.

It will be appreciated from the above-described process that none of the ingredients used is of a toxic character. Furthermore, very sharp impressions or etchings can be secured, possessing a high fidelity to the type or stamp that is employed. The ozokerite tilm 11 ordinarily cannot be used alone in that it does not afford sufficient protection. lt appears to be porous to cupric chloride so that areas besides the wanted areas may be etched therethrough. The objection to using the gilsonite layer 12 alone is that this layer, although frequently used as a standard ground, is not conducive to securing sharp impressions.

While other copper salts might be employed such as for example copper sulphate in lieu of the cupric chloride, I nd that the action or ionic exchange is comparatively slow when compared with the action of an aqueous solution of cupric chloride. By neutralizing or rendering inactive cupric chloride by the application of the ammonia, the ionic exchange is caused to stop and consequently, the etching into the plate is immediately discontinued.

While the invention has been described in conjunction with the etching of hardened ferrie metal thickness gauge blades, it will be readily appreciated that it is not restricted thereto but may be employed on ferrie articles which are not hardened and may be employed on other metallic articles such as those formed of aluminum and aluminum alloys. In all instances, it is of course desirable that the surface on which the design or indicia is to be applied be brightened or polished to facilitate the ionic exchange.

The ozokerite possesses high dielectric or electrical insulation properties and as such, apparently resists ionic exchange taking place therethrough except where the metal to be etched is left exposed. Natural ceresin is distilled from the mineral ozokerite and can be employed in lieu thereof. While there is available an articial ceresin, this product is inferior to the natural product and l, consequently, prefer the natural product.

Various changes may be made in the details of the method without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

l. The method of etching a metal of the group consisting of ferrous metals, aluminum, and aluminum alloys i0 which consists of applying a thin tilm of ozokerite to the article to be etched, applying thereover a thin film of gilsonite, applying a die to the two layers to extract from the ground produced thereby portions of the ground in conformity with the shape of the die, applying to the ground and that portion of the metal exposed by the removal of a portion of the ground a solution of a metallic salt capable of having an ionic exchange with the metal of the article to be etched, rendering inactive the solution of the metallic saltand removing the ground and the deposited metal from the metal thus etched.

2. The method of etching a metal of the group consisting of ferrous metals, aluminum, and aluminum alloys which consists of applying a thin lm of ozokerite to the article to be etched, applying thereover a thin film of gilsonite, applying a die to the two layers to extract from the ground produced thereby portions of the ground in conformity with the shape of the die, applying to the ground and that portion of the metal exposed by the removal of the portion of the ground an aqueous solution of a copper salt causing an ionic exchange to take place between the solution and the metal to be etched, rendering inactive the solution, and removing the ground and the deposited metal from the metal thus etched.

3. The method of etching a metal of the group consisting of ferrous metals, aluminum, and aluminum alloys which consists of applying a thin film of ozokerite to the article to be etched, applying thereover a thin film of gilsonite, applying a die to the two layers to extract from the ground produced thereby portions of the ground in conformity with the shape of the die, applying to the ground and to the portion of the metal exposed by the removal of a portion of the ground an aqueous solution of cupric chloride and a wetting agent, adding ammonia to the solution after an ionic exchange has taken place between the solution and the metal to be etched, and removing the ground and deposited metal from the metal thus etched.

Baynes Feb. 28, 1888 Meulendyke lune l2, 1951 

1. THE METHOD OF ETCHING A METAL OF THE GROUP CONSISTING OF FERROUS METALS, ALUMINUM, AND ALUMINUM ALLOYS WHICH CONSISTS OF APPLYING A THIN FILM OF OZOKERITE TO THE ARTUCKE TO BE WTCHED, APPLYING THEREOVER A THIN FILM OF GILSONITE, APPLYING A DIE TO THE TWO LAYERS TO EXTRACT FROM THE GROUND PRODUCED THEREBY PORTIONS OF THE GROUND IN CONFORMITY WITH THE SHAPE OF THE DIE, APPLYING TO THE GROUND AND THAT PORTION OF THE METAL EXPOSED BY THE REMOVAL OF A PORTION OF THE GROUP A SOLUTION OF A METALLIC SALT CAPABLE OF HAVING AN IONIC EXCHANGE WITH THE METAL OF THE ARTICLE TO BE ETECHED, RENDERING INACTIVE THE SOLUTION OF THE METALLIC SALT AND REMOVING THE GROUND AND THE DEPOSITED METAL FROM THE METAL THUS ETCHED. 